Reversible rotation gearbox and applications thereof

ABSTRACT

A gearbox includes a planetary gear assembly, a first gear assembly, and a second gear assembly. The first gear assembly is engaged to provide a first rotational input to the planetary gear assembly when an input shaft is rotating in a first direction and is disengaged when the input shaft is rotating in a second direction. The second gear assembly provides a second rotational input to the planetary gear assembly when the input shaft is rotating in the first direction and provides a third rotational input to the planetary gear assembly when the input shaft is rotating in the second direction.

CROSS REFERENCE TO RELATED PATENTS—NOT APPLICABLE STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT—NOT APPLICABLE INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC—NOT APPLICABLE BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates to motors and more particularly to a reversible rotation gearbox for use with a motor.

Description of Related Art

As is known, there are various types of electric motors and an almost endless variety of uses for them. For instances, an electric motor may be an AC motor (e.g., synchronous or induction), a servomotor, a DC motor, or an electrostatic motor (e.g., magnetic motor). Regardless of the type, size, shape, and power level of an electric motor may vary greater; it generally includes a stator and a rotor. The stator, or rotor, generates a magnetic field, which causes motion of the other, which causes an output shaft to rotate. Note that a gearbox may be used to generate a higher or lower rotation output speed than that of the motor's output shaft.

As is further known, an electric motor may be used in applications that range from micro-mechanical systems (MEMS), to food processing equipment, to household appliances, to power tools, to automobiles, to toys, to large manufacturing equipment, etc. In many applications, an electric motor is required to reverse its direction of rotation (e.g., rotate clockwise and counterclockwise). For an AC motor, its inputs are changed (e.g., lines switched, different capacitor connection, etc.) to change the direction of the output shaft rotation. While this allows the direction of rotation to change, it does not allow the speed of rotation to change. If a change in speed is needed, a transmission is generally required.

In a DC motor, a DC controller controls the voltage level and polarity of a DC voltage provided to the DC motor. This allows the DC motor to produce a higher rotational speed in one direction than in the other direction, which is beneficial for garage door openers that allow the garage door to open faster than it closes.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a block diagram of an embodiment of a gearbox in accordance with the present invention;

FIG. 2 is a block diagram of an example of operation of a gearbox in accordance with the present invention;

FIG. 3 is a block diagram of another example of operation of a gearbox in accordance with the present invention;

FIG. 4 is a block diagram of another embodiment of a gearbox in accordance with the present invention;

FIG. 5 is a block diagram of an embodiment of a motor-gearbox in accordance with the present invention; and

FIG. 6 is a block diagram of another embodiment of a gearbox in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a block diagram of an embodiment of a gearbox 10 that includes a planetary gear assembly 12 (e.g., simple or compound), a first gear assembly 14, and a second gear assembly 16. The first and second gear assemblies 14 and 16 are coupled to an input shaft (e.g., a shaft of a motor) and the first gear assembly 14 is coupled to a sun shaft 18 of the planetary gear assembly 12, which includes, or is coupled to, an output shaft 54.

In an example of operation, when the input shaft is rotating in a first direction (e.g., clockwise or counterclockwise), the first and second gear assemblies 14 and 16 are engaged, or locked. As such, the first gear assembly 14 applies a force to the sun shaft 18, causing it to rotate. The second gear assembly 16 applies a force to the planetary gear assembly 12, causing the output shaft 54 to rotate in a first output direction (e.g., clockwise or counterclockwise).

As a further example of operation, when the input shaft is rotating in a second direction (e.g., opposite to that of the first direction, the first gear assembly 14 is disengaged, thus not applying a force to the sun shaft 18, and the second gear assembly 16 is engaged. In this mode of operation, the second gear assembly 16 is providing a force to the planetary gear assembly 12, causing the output shaft 54 to rotate in an opposite direction. As will be discussed in greater detail with reference to one or more of the remaining figures, the output shaft rotates at a different speed (e.g., faster or slower) than when the input shaft is rotating in the first direction due to a planet gear carrier of the planetary gear assembly 12.

FIG. 2 is a block diagram of an example of operation of the gearbox 10 when the input shaft is rotating in the first direction 20. In this example, the first and second gear assemblies 14 and 16 are engaged. The first gear assembly 14 generates a first rotational input 22 that causes the sun shaft 18 to rotate. The second gear assembly 16 generates a second rotational input 24 that causes the planetary gear assembly 12 to rotate. The complimentary rotational inputs 22 and 24 drive the planetary gear assembly 12 to produce an output shaft 54 rotation in a first output direction 25 at a first speed. Note that direction of the first and second rotational inputs 22 and 24 may be in the same direction as the first shaft rotation direction 20 or in the opposite direction. Further note that the speed of the first and second rotational inputs 22 and 24 may be at the same speed as each other and as the speed of the input shaft; may be at the same speed as each other but at a different speed than that of the input shaft; may be at different speeds than each other, with one of the speeds being the same speed as that of the input shaft; or may be at different speeds than each other, with each speed being different than the speed of the input shaft.

FIG. 3 is a block diagram of another example of operation of the gearbox 10 when the input shaft is rotating in a second direction 26. In this example, the first gear assembly 14 is disengaged and the second gear assembly 16 is engaged. The second gear assembly 16 generates a third rotational input 28 drives the planetary gear assembly 12 to produce an output shaft 54 rotation in a second output direction 27 at a second speed.

The second output direction 27 is opposite to that of the first output direction 25 and the second output speed is different (e.g., faster or slower) than the first output speed.

FIG. 4 is a block diagram of another embodiment of a gearbox 10 that includes a planetary gear assembly 12, a first gear assembly 14, and a second gear assembly 16. The planetary gear assembly 12 includes a plurality of planet gears 46-48 (e.g., two or more), the sun shaft 18, a ring gear assembly 40 (which includes an outer ring gear 42 and an inner ring gear 44), and a planet gear carrier 50. The first gear assembly 14 includes an input gear 30, an idler gear 32, a sun shaft gear 34, and a clutch 36 (which is shown to be part of the input gear 30, but could be part of sun shaft gear 34). The second gear assembly 16 includes an input gear 38. The planet gear carrier 50 (e.g., a planet carrier) includes a clutch 52, an output shaft 54, and planet gear couplers 55 (e.g., gears, shafts, etc.). Note that the clutch 36 may be a clutch, a ratchet, or any other mechanical device that is engaged in one direction and that is disengaged in an opposite direction.

In an example of operation, when the input shaft is rotating in the first direction at a given speed, the one-way clutch 36 of the input gear 30 is engaged, causing it to rotate in accordance with the rotation of the input shaft. The input gear 30 drives the idler gear 32, which, in turn, drives the sun shaft gear 34. The sun shaft gear 34 is mechanically coupled (e.g., welded, press fitted, screwed, bolted, glued, clamped, in physical contact via gear teeth, etc.) to the sun shaft 18 causing it to rotate in the same direction as the input shaft.

The sun shaft 18 is mechanically coupled to the planet gears 46-48, causing them to rotate in a first complimentary direction (e.g., a direction based on the gearing of the first, second, and ring gear assemblies and the first rotation of the input shaft). For instance, the sun shaft 18 includes a sun gear where its teeth mechanically couple to gear teeth of the planet gears 46-48. In addition to the sun shaft driving the planet gears 46-48, the inner ring gear 44 of the ring gear assembly 40 drives the planet gears 46-48. The inner ring gear 44 rotates in accordance with the rotation of the outer ring gear 42, which is driven by the input gear 38 of the second gear assembly 16.

To insure that the inner ring gear 44 and the sun shaft 18 are applying desired rotational forces on the planet gears 46-48, the linear speed (i.e., distance traversed in a given time period) of the sun shaft 18 is different (e.g., faster or slower) than the linear speed of the inner ring gear 44. Accordingly, the gear ratio of the input gear 30, the idler gear 32, and the sun shaft gear 34 is select to produce the desired linear speed of the sun shaft 18 and the gear ratio of the input gear 38 of the second gear assembly 16, the outer ring gear 42, and the inner ring gear 44 is select to produce the desired linear speed of the inner ring gear 44.

With the sun shaft 18 rotating in the present direction, the clutch 52 of the planet gear carrier 50 is disengaged. In this manner, the sun shaft 18 and the input gear 38 are the inputs of the ring gear assembly 12 causing the output shaft 54 of the carrier 50 to rotate in a first output direction (e.g., clockwise or counterclockwise) at a first output speed.

In another example of operation, when the input shaft is rotating in the second direction at the given speed, the one-way clutch 36 of the input gear 30 is disengaged. The input gear 38 of the second gear assembly 16 is engaged to rotate the outer ring gear 42 of the ring gear assembly 40, which causes the planet gear carrier 50 to rotate in a complimentary second direction (e.g., a direction based on the gearing of the second and ring gear assemblies and the second rotation of the input shaft). For instance, the individual planet gears do not rotate around their individual axis, but the planet gear carrier 50 rotates based on rotation of the sun shaft 18, which causes the individual planet gears to rotate.

In this example, the clutch 52 of the planet gear carrier 50 is engaged. In this manner, the outer ring gear 42 is the input of the ring gear assembly 12 causing the output shaft 54 of the carrier 50 to rotate in a second output direction (e.g., clockwise or counterclockwise) at a second output speed. Note that the second output direction is opposite to the first output direction and the second speed is different (e.g., greater than or less than) the first output speed.

In a further example, the first direction of the rotation of the input shaft is a clockwise direction and the second direction of the rotation of the input shaft is a counterclockwise direction. Accordingly, the second rotational input includes a clockwise direction rotation and the third rotational input includes a counterclockwise direction rotation.

In various embodiments of the gearbox 10, the gear assemblies 12-16 may include more or less gears than shown in FIG. 4 to achieve a desire gear ratio, a desired output power, a desired first output speed, and a desired second output speed. In addition, the size, number of teeth, and material of each gear within each assembly 12-16 may vary based on the application. For instance, if the gearbox is used in a MEMS application, the gears will be micrometers to millimeters in size and composed of silicon or other MEMS material. Alternatively, if the gearbox is used in an industrial application, the gears may be fractions of meters to tens of meters in size and composed of steel, plastic, or other industrial acceptable material.

FIG. 5 is a block diagram of an embodiment of a motor-gearbox that includes the gearbox 10 and a motor 60. The motor includes a shaft 62, which is the input shaft to the gearbox. The motor 60 may be a reversible AC motor such that, by changing its inputs, the rotation of the shaft 62 may change direction, but, in either direction, will be of a constant speed.

The gearbox is mechanically couplable to the motor (e.g., via the shaft 62) and includes the planetary gear assembly 12 that includes a planet gear carrier, the first gear assembly 14, and the second gear assembly 16. The first gear assembly 14 is engaged to provide a first rotational input to the planetary gear assembly 12 when the motor shaft 62 is rotating in a first direction and is disengaged when the motor shaft 62 is rotating in a second direction. The second gear assembly 16 provides a second rotational input to the planetary gear assembly 12 when the motor shaft 62 is rotating in the first direction and provides a third rotational input to the planetary gear assembly 12 when the motor shaft 62 is rotating in the second direction.

When the first gear assembly 14 is engaged, a clutch of the planet gear carrier is disengaged. In this manner, the sun shaft 18 and the second gear assembly 16 are the inputs of the planetary gear assembly 12 causing the output shaft of the carrier to rotate in a first output direction (e.g., clockwise or counterclockwise) at a first output speed. When the first gear assembly is disengaged, the clutch of the planet gear carrier is engaged. In this manner, the outer ring gear 42 is the input of the planetary gear assembly 12 causing the output shaft of the carrier to rotate in a second output direction (e.g., clockwise or counterclockwise) at a second output speed.

FIG. 6 is a block diagram of another embodiment of a gearbox 10 includes a planetary gear assembly 12, a first gear assembly 14, a second gear assembly 16, and a planet gear carrier 50. The first gear assembly 14 is mechanically couplable (e.g., welded, press fitted, screwed, bolted, glued, clamped, in physical contact via gear teeth, etc.) to the planetary gear assembly 12 through sun shaft 18 and to an input shaft 62. The first gear assembly 14 and includes one or more gears, wherein one of the one or more gears includes a first one-way clutch. The second gear assembly 16 is mechanically couplable to the planetary gear assembly 12 and to the input shaft 62 and includes one or more gears.

The planet gear carrier 50 is mechanically couplable to planetary gear assembly 12 and includes an output shaft 54 and second one-way clutch 52, which is coupled to the sun shaft 18. When the input shaft is rotating in the first direction at a speed, the one-way clutch 36 is engaged and the one-way clutch 52 is disengaged such that the output shaft rotates in a first output direction at a first speed. When the input shaft is rotating in the second direction at the speed, the one-way clutch 36 is disengaged and the one-way clutch 52 is engaged such that the output shaft 54 rotates in a second output direction at a second speed.

As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “operable to” or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item. As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1.

As may also be used herein, the terms “processing module”, “processing circuit”, and/or “processing unit” may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing module, module, processing circuit, and/or processing unit may be, or further include, memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of another processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the Figures. Such a memory device or memory element can be included in an article of manufacture.

The present invention has been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claimed invention. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality. To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claimed invention. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.

The present invention may have also been described, at least in part, in terms of one or more embodiments. An embodiment of the present invention is used herein to illustrate the present invention, an aspect thereof, a feature thereof, a concept thereof, and/or an example thereof. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process that embodies the present invention may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.

The term “module” is used in the description of the various embodiments of the present invention. A module includes a processing module, a functional block, hardware, and/or software stored on memory for performing one or more functions as may be described herein. Note that, if the module is implemented via hardware, the hardware may operate independently and/or in conjunction software and/or firmware. As used herein, a module may contain one or more sub-modules, each of which may be one or more modules.

While particular combinations of various functions and features of the present invention have been expressly described herein, other combinations of these features and functions are likewise possible. The present invention is not limited by the particular examples disclosed herein and expressly incorporates these other combinations. 

What is claimed is:
 1. A gearbox comprises: a planetary gear assembly; a first gear assembly that is: engaged to provide a first rotational input to the planetary gear assembly when an input shaft is rotating in a first direction; and disengaged when the input shaft is rotating in a second direction; and a second gear assembly that: provides a second rotational input to the planetary gear assembly when the input shaft is rotating in the first direction; and provides a third rotational input to the planetary gear assembly when the input shaft is rotating in the second direction.
 2. The gearbox of claim 1, wherein the planetary gear assembly comprises: a plurality of planet gears; a sun shaft mechanically coupled to the plurality of planet gears and to the first gear assembly; a planet gear carrier mechanically coupled to the plurality of planet gears; and a ring gear assembly mechanically coupled to the plurality of planet gears and to the second gear assembly, wherein the first and second rotation inputs rotate the planet gear carrier in a first output direction and wherein the third rotation input rotates the plurality of planet gears, which rotates the planet gear carrier in a second output direction.
 3. The gearbox of claim 2, wherein the planet gear carrier comprises: a clutch that is engaged when the input shaft is rotating in the second direction and is disengaged when the input shaft is rotating in the first direction, wherein, when the input shaft is rotating in the first direction, the planet gear carrier rotates in the first output direction at a first speed and, when the input shaft is rotating in the second direction, the planet gear carrier rotates in the second output direction at a second speed.
 4. The gearbox of claim 2, wherein the ring gear assembly comprises: an inner ring gear mechanically couplable to the plurality of planet gears; and an outer ring gear mechanically couplable to the second gear assembly.
 5. The gearbox of claim 1, wherein the first gear assembly comprises: an input gear mechanically couplable to the input shaft; an idler gear mechanically couplable to the input gear; and a sun shaft gear mechanically couplable to the idler gear and to a sun shaft of the planetary gear assembly, wherein one of the input gear and the sun shaft gear includes a one-way clutch that is engaged when the input shaft is rotating in the first direction and is disengaged when the input shaft is rotating in the second direction.
 6. The gearbox of claim 1, wherein the second gear assembly comprises: an input gear mechanically couplable to the input shaft and to the ring gear assembly.
 7. A gear motor comprises: a motor having a motor shaft; and a gearbox mechanically couplable to the motor, the gearbox including: a planetary gear assembly; a first gear assembly that is: engaged to provide a first rotational input to the planetary gear assembly when the motor shaft is rotating in a first direction; and disengaged when the motor shaft is rotating in a second direction; and a second gear assembly that: provides a second rotational input to the planetary gear assembly when the motor shaft is rotating in the first direction; and provides a third rotational input to the planetary gear assembly when the motor shaft is rotating in the second direction.
 8. The gear motor of claim 7, wherein the planetary gear assembly comprises: a plurality of planet gears; a sun shaft mechanically coupled to the plurality of planet gears and to the first gear assembly; a planet gear carrier mechanically coupled to the plurality of planet gears; and a ring gear assembly mechanically coupled to the plurality of planet gears and to the second gear assembly, wherein the first and second rotation inputs rotate the planet gear carrier in a first output direction and wherein the third rotation input rotates the plurality of planet gears, which rotates the planet gear carrier in a second output direction.
 9. The gear motor of claim 8, wherein the planet gear carrier comprises: a clutch that is engaged when the input shaft is rotating in the second direction and is disengaged when the input shaft is rotating in the first direction, wherein, when the input shaft is rotating in the first direction, the planet gear carrier rotates in the first output direction at a first speed and, when the input shaft is rotating in the second direction, the planet gear carrier rotates in the second output direction at a second speed.
 10. The gear motor of claim 8, wherein the ring gear assembly comprises: an inner ring gear mechanically couplable to the plurality of planet gears; and an outer ring gear mechanically couplable to the second gear assembly.
 11. The gear motor of claim 7, wherein the first gear assembly comprises: an input gear mechanically couplable to the motor shaft; an idler gear mechanically couplable to the input gear; and a sun shaft gear mechanically couplable to the idler gear and to a sun shaft of the planetary gear assembly, wherein one of the input gear and the sun shaft gear includes a one-way clutch that is engaged when the input shaft is rotating in the first direction and is disengaged when the input shaft is rotating in the second direction.
 12. The gear motor of claim 7, wherein the second gear assembly comprises: an input gear mechanically couplable to the motor shaft and to the ring gear assembly.
 13. A gearbox comprises: a planetary gear assembly that includes a first one-way clutch and an output shaft; a first gear assembly mechanically couplable to the planetary gear assembly and to an input shaft, wherein the first gear assembly includes a second one-way clutch; and a second gear assembly mechanically couplable to the planetary gear assembly and to the input shaft, wherein, when the input shaft is rotating in the first direction, the second one-way clutch is engaged and the first one-way clutch is disengaged such that the output shaft rotates in a first output direction at a first speed and, when the input shaft is rotating in the second direction at the speed, the second one-way clutch is disengaged and the first one-way clutch is engaged such that the output shaft rotates in a second output direction at a second speed.
 14. The gearbox of claim 13, wherein the planetary gear assembly comprises: a plurality of planet gears; a sun shaft mechanically coupled to the plurality of planet gears and to the first gear assembly; a planet gear carrier mechanically coupled to the plurality of planet gears, wherein the planet gear carrier includes the first one-way clutch coupled to the sun shaft; and a ring gear assembly mechanically coupled to the plurality of planet gears and to the second gear assembly.
 15. The gearbox of claim 14, wherein the ring gear assembly comprises: an inner ring gear mechanically couplable to the plurality of planet gears; and an outer ring gear mechanically couplable to the second gear assembly.
 16. The gearbox of claim 13, wherein the first gear assembly comprises: an input gear mechanically couplable to the input shaft; an idler gear mechanically couplable to the input gear; a sun shaft gear mechanically couplable to the idler gear; and a sun shaft mechanically couplable to the sun shaft gear and to the planetary gear assembly, wherein one of the input gear, the idler gear, and the sun shaft gear includes the second one-way clutch.
 17. The gearbox of claim 13, wherein the second gear assembly comprises: an input gear mechanically couplable to the input shaft and to the ring gear assembly. 